AQA · GCSE · Computer Science
Course version: 8525 · Version from Sept 2020
Understand that processors execute machine code and that each type of…
Full specification wording
Classification of programming languages and translators: understand that processors execute machine code and that each type of processor has its own specific machine code instruction set
A processor carries out instructions written in machine code, the binary patterns built into its design.
Checked against the AQA 8525 specification (opens in a new tab) on .
- Point 6 of 19
Study notes
From the checked teaching notes for this specification point.
The idea
A processor carries out instructions written in machine code, the binary patterns built into its design. Each type of processor, such as a particular CPU family or a microcontroller, recognises only its own specific machine code instruction set: the fixed collection of instructions it can decode and execute, with defined binary patterns for operations like loading, adding or storing. This is why a program compiled for one processor type may not run on another, because the binary instructions mean something different or are not recognised. Assembly language is tied to the same instruction set, so an assembler targets a specific processor. Understanding this explains why software is built or compiled for a particular platform and why portability between different processors is not automatic.
What earns the marks
- Processors execute machine code, which consists of binary instructions.
- Each type of processor has its own specific machine code instruction set.
- The instruction set is the fixed set of binary instructions a given processor can decode and execute.
- Because instruction sets differ, machine code written for one processor type may not run on another.
- Assembly language and its assembler are tied to a particular processor's instruction set.
Common mistakes and how to put them right
Thinking all processors understand the same machine code.
Put it right by stating each processor type has its own instruction set.
Believing machine code is translated again at run time.
Put it right by explaining the processor executes machine code directly.
Assuming a program runs unchanged on any device.
Put it right by linking portability problems to differing instruction sets.
Exam tips
- Use the phrase 'instruction set' precisely to mean the processor's own set of binary instructions.
- When explaining portability, connect it explicitly to differences between instruction sets.
- Keep the focus on the processor executing machine code rather than on high-level language translation.
Try the lesson
The start of the Classification of programming languages and translators: understand that processors execute machine code and that each type of processor has its own specific machine code instruction set lesson, made from checked teaching notes for this specification point.
Have a go first
Which form of program can a processor carry out directly without first being translated?
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